Physician follow-up of patients with laboratory abnormalities in 12 commonly obtained blood tests was studied in the ambulatory setting. Nineteen white male physicians had 166 patients with 279 abnormal results. Overall, 38.6 percent of patients had abnormalities followed up. White male patients had a 56.6 percent follow-up, while other patients (black males, white and black females) had a 31.7 percent follow-up rate (P = .006). These higher rates for white males persisted when controlling for the effects of patient age, Medicaid status, type of medical problem for which laboratory tests were obtained, number of abnormalities per patient, degree of abnormality of the laboratory result, and physician year of residency. The scientific rationale for the higher follow-up rates for white males than for other patients was not elucidated by the present study.